?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Adc&rft.title=Direct+evidence+for+local+oscillatory+current+sources+and+intracortical+phase+gradients+in+turtle+visual+cortex&rft.creator=Prechtl%2C+James+C.&rft.creator=Bullock%2C+T.H.&rft.creator=Kleinfeld%2C+David.&rft.subject=Behavioral+Neuroscience&rft.subject=Behavioral+Biology&rft.subject=Neurophysiology&rft.subject=Neurophysiology&rft.description=Visual+stimuli+induce+oscillations+in+the+membrane+potential+of+neurons+in+cortices+of+several+species.+In+turtle%2C+these+oscillations+take+the+form+of+linear+and+circular+traveling+waves.+Such+waves+may+be+a+consequence+of+a+pacemaker+that+emits+periodic+pulses+of+excitation+that+propagate+across+a+network+of+excitable+neuro-nal+tissue+or+may+result+from+continuous+and+possibly+reconfigu-rable+phase+shifts+along+a+network+with+multiple+weakly+coupled+neuronal+oscillators.+As+a+means+to+resolve+the+origin+of+wave+propagation+in+turtle+visual+cortex%2C+we+performed+simultaneous+measurements+of+the+local+field+potential+at+a+series+of+depths+throughout+this+cortex.+Measurements+along+a+single+radial+pen-etration+revealed+the+presence+of+broadband+current+sources%2C+with+a+center+frequency+near+20+Hz+(+g+band)%2C+that+were+activated+by+visual+stimulation.+The+spectral+coherence+between+sources+at+two+well-separated+loci+along+a+rostral%C2%96+caudal+axis+revealed+the+pres-ence+of+systematic+timing+differences+between+localized+cortical+oscillators.+These+multiple+oscillating+current+sources+and+their+timing+differences+in+a+tangential+plane+are+interpreted+as+the+neuronal+activity+that+underlies+the+wave+motion+revealed+in+previous+imaging+studies.+The+present+data+provide+direct+evidence+for+the+inference+from+imaging+of+bidirectional+wave+motion+that+the+stimulus-induced+electrical+waves+in+turtle+visual+cortex+corre-spond+to+phase+shifts+in+a+network+of+coupled+neuronal+oscillators.&rft.date=2000-01&rft.type=Journal+(Paginated)&rft.type=PeerReviewed&rft.format=application%2Fpdf&rft.identifier=http%3A%2F%2Fcogprints.org%2F138%2F3%2Fprechtl_csd.pdf&rft.identifier=++Prechtl%2C+James+C.+and+Bullock%2C+T.H.+and+Kleinfeld%2C+David.++(2000)+Direct+evidence+for+local+oscillatory+current+sources+and+intracortical+phase+gradients+in+turtle+visual+cortex.++%5BJournal+(Paginated)%5D+++++&rft.relation=http%3A%2F%2Fcogprints.org%2F138%2F